Typically, solid oxide fuel cells (SOFC) employ an electrolyte of ion-conductive solid oxide such as stabilized zirconia. The electrolyte is interposed between an anode and a cathode to form an electrolyte electrode assembly (MEA). The electrolyte electrode assembly is sandwiched between a pair of separators (bipolar plates). In use, generally, predetermined numbers of the separators and the electrolyte electrode assemblies are stacked together to form a fuel cell stack.
In the fuel cell, in order to supply a fuel gas such as a hydrogen-containing gas and an oxygen-containing gas such as the air to the anode and the cathode of the electrolyte electrode assembly, respectively, a fuel gas channel and an oxygen-containing gas channel are formed along surfaces of the separator.
For example, as shown in FIG. 17, a flat plate stack type fuel cell disclosed in Japanese Laid-Open Patent Publication No. 2008-251236 includes a separator 1 stacked on a power generation cell. The separator 1 includes an interconnection part 2 provided at a central portion thereof where power generation cells and current collectors are stacked together, and a pair of arms 3a, 3b supporting the interconnection part 2 at opposite marginal portions. Each of the arms 3a, 3b has a narrow stripe shape with small clearance interposed between each arm 3a, 3b and the interconnection part 2, so that the arms 3a, 3b have flexibility for allowing displacement in the stacking direction.
The interconnection part 2 has a function to supply oxygen-containing gas and fuel gas to the power generation cells, and an oxygen-containing gas channel 4 as a passage of the oxygen-containing gas (air) and a fuel gas channel 5 as a passage of the fuel gas are formed in the interconnection part 2.
An oxygen-containing gas hole 6 and a fuel gas hole 7 extend through ends of the arms 3a, 3b in the thickness direction, respectively. The oxygen-containing gas hole 6 is connected to the oxygen-containing gas channel 4 through one arm 3a, and the fuel gas hole 7 is connected to the fuel gas channel 5 through the other arm 3b. 
The oxygen-containing gas and the fuel gas flow from the oxygen-containing gas hole 6 and the fuel gas hole 7 through the oxygen-containing gas channel 4 and the fuel gas channel 5. Then, the oxygen-containing gas and the fuel gas are ejected from gas ejection ports 4a, 5a at ends of the gas channels provided at the center of the interconnection part 2 toward the center of the electrode surfaces of the power generation cells.